B8ZS (Bipolar 8 Zero
Substitution) - a technique used to satisfy the ones density
requirements of digital T-carrier facilities in the public network while
allowing 64 Kbps clear channel data. Strings of eight consecutive zeroes are
replaced by an eight-bit code representing two intentional bipolar pulse code
Backbone - The main
connectivity device of a distributed system. All systems that have connectivity
to the backbone connect to each other. This does not stop systems from setting
up private arrangements with each other to bypass the backbone for cost,
performance, or security.
Background Noise -
The total system noise in the absence of information transmission, independent
of the presence or absence of a signal.
Backplane - High-speed
communications line to which individual components are connected. In
multi-plane fabric switches, the backplane allows for inter-fabric connections
and timing distribution without the need for physical cables.
Baffle - A mounting
board or screen which separates acoustic power at the back of a loudspeaker
cone from the power directly emitted from the front of the loudspeaker. Baffles
improve bass response by increasing the length of the path difference between
the two sources of sound. Also, a heat displacing device mounted between
equipment in a rack or enclosure to direct heat from a unit away from equipment
mounted above it.
Bandwidth - Usually
identifies the capacity or amount of data that can be sent through a given
circuit; may be user-specified in a PVC.
Bar Code - Lines of
varying width printed on the label of a product. The bar code is designed to be
read optically by a data capturing device.
Bare Wire -
Battery or Batteries
- A DC voltage source made up of one or more cells that convert chemical energy
into electrical power. The combination of several cells is more correctly
referred to as the battery (singular). The cells themselves are sometimes
erroneously referred to as batteries.
Battery Acid -
Dilute sulfuric acid used as electrolyte in a lead/acid storage
Battery Alarm -
Alarm indicating that there is a fault in a main battery circuit.
Battery Backup - A
battery which provides power to equipment during the absence of commercial AC.
- The capacitance of a battery plant which acts as a filter.
Battery Eliminator -
A device which has a rectifier and a filter. This device will convert AC power
into the correct DC voltages necessary to drive a telephone system. Such a
battery eliminator or power supply should deliver “clean” power, i.e. with
little “noise” and of low impedance.
Battery Noise -
Noise which is sometimes fed into telephone circuits on the DC power supply
leads, e.g. a low hum from the rectifier or impulse noise from relay contact
Battery Pair - A
pair of wires used to carry DC power which is tapped from the central office
Battery Reserve -
The length of time for which a storage battery can provide DC power within the
circuit voltage limits of the load equipment.
Battery Separator -
Sheets of nonconducting porous material between positive and negative plates in
a storage battery. They prevent short circuits caused by plates bending and
Battery Stand or Rack
- A rigid structure used to accommodate a group of cells. Available for
different seismic zones.
Battery String or Battery
Plant - A DC voltage source made up of one or more cells that convert
chemical energy into electrical power.
Baud - Unit of
signaling speed. The speed in baud is the number of discrete conditions or
signal events per second. If each signal event represents only one bit, the
baud rate is the same as bps; if each signal event represents more than one bit
(such as a digit), the baud rate is smaller than bps.
BBC (Broadband Bearer
Capability) - Indicates request for connection-oriented service that
will provide interworking (i.e. DS1 emulation) ATM only, or VP service (for
“B” Carrier - See
Wireline Cellular Company.
BCOB (Broadband Connection
Oriented Bearer) - Information in the SETUP message that indicates the
type of service requested by the calling user.
BCOB-A (Bearer Class A)
- Indicated by ATM end user in SETUP message for connection-oriented, constant
bit rate service. The network may perform internetworking based on AAL
information element (IE).
BCOB-C (Bearer Class C)
- Indicated by ATM end user in SETUP message for connection-oriented, variable
bit rate service. The network may perform internetworking based on AAL
information element (IE).
BCOB-X (Bearer Class X)
- Indicated by ATM end user in SETUP message for ATM transport service where
AAL, traffic type and timing requirements are transparent to the network.
BD or BOD (Battery On
Discharge) - A discrete lead designation used to report a low battery
voltage condition. Initiation of the alarm is usually taken from the LV1 Lorain
Products plant setting. The low float setting on WECO coded plants that have
this feature can also be used for this alarm. The 326 and 111A coded plants,
designed to serve the ESS switching system, are arranged with a standard option
to provide this feature. The signal is taken from the higher level of a low
voltage battery condition and is used to forward an early warning that the
batteries are low, which implies that the batteries are being used to provide a
part or all of the plant demand.
BDCBB (Battery Distribution
Circuit Breaker Board - A bay containing panels equipped with circuit
breaker arrangements that distribute 24 volt or 48 volt battery.
BDFB (Battery Distribution
Fuse Board - A frame that accepts feeders from 24, 48, or 130 volt
battery plants and distributes the power through branch fuses to the load. It
is usually located near the equipment it serves.
BECN (Backward Explicit
Congestion Notification) - A Resource Management (RM) cell type
generated by the network or the destination, indicating congestion or
approaching congestion for traffic flowing in the direction opposite that of
the BECN cell.
Benchmark - A
standardized task to test the capabilities of various devices or organizations
against each other for performance.
Bending Radius -
The minimum allowable curvature of a cable before it is damaged. Very critical
in all aspects of cable laying, especially with under-carpet cabling and fiber
BER (Bit Error Rate)
- A measure of transmission quality. It is generally shown as a negative
exponent, (e.g., 10-7 which means 1 out of 107 bits are in error or 1 out of
10,000,000 bits are in error).
BES (Bursty Errored Seconds)
- a BES contains more than 1 and fewer than 320 path coding violation
error events, and no severely errored frame or AIS defects. Controlled slips
are not included in determining BESs.
Beta Test -
Typically the last step in the testing of a product before it is officially
released. A beta test is often conducted with customers in their offices.
BGP (Border Gateway
Protocol) - Used by gateways in an internet connecting autonomous
(router) networks. It is defined in RFC 1771.
B-ICI (B-ISDN Inter-Carrier
Interface) - An ITU-T defined specification for broadband switched
virtual connection between public networks.
Binary - A number
system where only two values or states are possible for a particular condition,
such as “ON” and “OFF” or “One” and “Zero.”
BIP (Bit Interleaved Parity)
- An error-detection technique in which character bit patterns are forced into
parity, so that the total number of one bits is always odd or always even. This
is accomplished by the addition of a one or zero bit to each byte, as the byte
is transmitted; at the other end of the transmission, the receiving device
verifies the parity (odd or even) and the accuracy of the transmission.
B-ISDN (Broadband Integrated
Services Digital Network) - A common digital network suitable for
voice, video, and high-speed data services running at rates beginning at 155
B-ISUP (Broadband ISDN
User’s Part) - A protocol used to establish, maintain and release
broadband switched network connections across a SS7/ATM network.
Bit - Abbreviation
for binary digit. A single binary digit of information represented as a 0
(zero) or 1 (one).
Bit Robbing - The
use of the least significant bit per channel in every sixth frame for
BITS (Building Integrated
Timing Supply) - The BITS is the master timing supply for an entire
building, which is a master clock and its ancillary equipment. The BITS
supplies DS1 and/or composite clock timing references for synchronization to
all other clocks and timing sources in that building.
Bit Stuffing - A
process in bit-oriented protocols where a zero is inserted into a string of
ones by the sender to prevent the receiver from interpreting valid user data
(the string of ones) as control characters (a Flag character for instance).
Blackout - A close
down of radio communications for security purposes. Also, a fade-out of radio
communications caused by ionospheric activity. Also, a complete loss of
Block Diagram - A
graphic way to show different elements of a program or process by the use of
squares, rectangles, diamonds, and various shapes connected by lines to show
what must be done, when it must be done, and what happens if it’s done this way
BN - A bit used to
identify whether an RM cell is Backward Explicit Congestion Notification cell
- A bayonet-locking connector used to terminate coaxial cables. BNC is also
referred to as Bayonet Network Connector.
BOC or RBOC (Bell Operating
Company) - The 22 regulated telephone companies of the former Bell
System, which was broken apart by divestiture. These companies were grouped
into seven Regional Holding Companies (RHCs). According to the terms of
divestiture, these companies must limit their activities to local telephone
service, directory service, customer premise equipment, cellular radio and any
other ventures that the Federal Court may approve from time to time.
Border Node - A
logical node that is in a specific peer group, and has at least one link that
crosses the peer group boundary.
BPDU (Bridge Protocol
Data Unit) - A message type used by bridges to exchange management and
bps (Bits per Second)
- A measure of speed in a serial transmission.
BPV (Bipolar Violation)
- an error event on a line in which the normal pattern of alternating high
(one) and low (zero) signals is disrupted. A bipolar violation is noted when
two high signals occur without an intervening low signal, or vice versa.
Breadboard - A
circuit board that is made by hand, usually in building a prototype.
Break Contacts -
Contacts which open when a relay is operated or a key thrown.
Bridge - a device
that expands a Local Area Network by forwarding frames between data link layers
associated with two separate cables, usually carrying a common protocol.
Bridges can usually be made to filter certain packets (to forward only certain
Bridge Rectifier -
A full-wave rectifier with four rectifying units arranged in a bridge so that
when AC is connected across one diagonal, DC is available across the other
Broadband - a
service or system requiring transmission channels capable of supporting rates
greater than the Integrated Services Digital Network (ISDN) primary rate.
Broadband Access -
an ISDN access capable of supporting one or more broadband services.
Broadcast - Data
transmission to all addresses or functions.
- a device that routes some protocols and bridges others based on configuration
Brownout - A
reduction in commercial voltage level that may be a result of an overload on
BSP (Bell System Practice)
- A standard or procedure specified by the Bell System.
Terminal Equipment) - An equipment category for B-ISDN which includes
terminal adapters and terminals.
Buffer - A data
storage medium used to compensate of a difference in rate of data flow or time
of occurrence of events when transmitting data from one device to another.
Building Alarms -
The group of alarms in a central office which cover alarm conditions for such
items as sump pumps, air dryers, heating and air conditioning.
Burn-In - To run
new devices and printed circuit cards, often at high temperatures, in order to
pinpoint early failures.
Bursty Second - A
second during which there were at least the set number of BES threshold event
errors but fewer than the set number of SES threshold event errors.
BUS (Broadcast and Unknown
Server) - in an emulated LAN, the BUS is responsible for accepting
broadcast, multicast, and unknown unicast packets from the LECs to the
broadcast MAC address (FFFFFFFFFFFF) via dedicated point-to-point connections,
and forwarding the packets to all of the members of the ELAN using a single
Bus Bar - Copper or
aluminum bars used to transmit or terminate AC or DC power.
Busy Hour Drain -
The average amount of current required by connected telephone equipment over a
period of one hour at the time of maximum use.
Busy Tone - Low
tone, interrupted once per second, indicating that the called line is busy.
Descriptive of an inverter plant status whereby the normal input source is
transferred through a static or mechanical switch to the alternate source.
Bypass Cabling -
Bypass cabling or relays are wired connections in a local area ring network
that permit traffic to travel between two nodes that are not normally wired
next to each other.
Byte - A
computer-readable group of bits (normally 8 bits in length).